Field of the Invention
The present invention relates to a polarizing plate and a method for manufacturing the polarizing plate.
Description of the Related Art
As a polarizing plate used for a liquid crystal display device or the like, a polarizing film including protective films bonded to both surfaces thereof is generally used. Examples of the polarizing film include a polarizing film obtained by adsorbing a dichroic material such as iodine or a dichroic dye to a polyvinyl alcohol-based film and further orienting the film by stretching. Examples of the protective film include a triacetyl cellulose film. A polyvinyl alcohol-based adhesive or the like is used to bond the protective film to the polarizing film.
The liquid crystal display device is often used for a long period of time under a high temperature condition or the like because of the wide usage of the liquid crystal display device. For example, the liquid crystal display device is often used for vehicle installation and a handheld terminal. As a result, the polarizing plate is also required to have reliability (durability) such that the polarizing plate suffers from no deterioration in optical property when the polarizing plate is placed under a high temperature condition or high temperature/high humidity conditions.
However, since the triacetyl cellulose film used for the protective film is water-vapor permeable (has a high water-vapor permeability), the optical property of the polarizing film and the adhesion property of an adhesive are deteriorated by the absorption of moisture, which may cause display unevenness. As a countermeasure for this problem, a technique is proposed, in which an adhesive layer for bonding a protective film to a polarizing film is dried at 40 to 70° C., and a ratio of absorbance of the polarizing film at 296 nm to absorbance thereof at 480 nm is set at 1.65 or less to improve durability in a humidified environment (for example, see Patent Document 1).